Portable fire alarm unit



Jan. 2, 1962 R. RUBIN 3,01

PORTABLE FIRE ALARM UNIT Filed March 9, 1959 g 54 52 Fig. 2

3 P lB L as INVENTOR. LEONARD R. RUBIN M. SLJML United States Patent3,015,811 PORTABLE FIRE ALARM UNIT Leonard R. Rubin, Wynnewood, Pa.,assignor to Harry Rubin & Sons Inc., Philadelphia, Pa., a corporation ofPennsylvania Filed Mar. 9, 1959, Ser. No. 797,958 2 Claims. (Cl.340-227) It is another object of-the present invention to provide aself-contained fire alarm unit which can be easily mounted on a wall,ceiling, or other surface of a room without the necessity for-electricwiring or the need of special tools or special skill.

It is still another object of the present invention to provide aportable fire alarm unit which is of simple constructionso that thebatteries -for operating the unit can be easily and quickly replacedwhen necessary.

It is a further object of the present invention to provide a portablefire alarm unit which can be easily tested from time-to-time todetermine whether the unit is in good operating condition.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in thedrawings a form which is presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIGURE 1 is a perspective view of the portable fire alarm unit of thepresent invention mounted on a wall or like surface.

FIGURE 2 is a sectional view, partly in elevation, of the portable firealarm unit of the present invention.

FIGURE 3 is an elevational view taken along line 33 of FIGURE 2.

Referring initially to FIGURE 2, the portable fire alarm unit of thepresent invention is generally designated as 10.

Fire alarm unit 10 comprises a hollow, cylindrical, metal casing 12having a bottom wall 14. The top end portion 16 of the casing 12 isflared radially outwardly, and is threaded on its external surface.Casing 12 has a keyhole slot 18 therethrough just below the flared topend portion 16 of the casing 12. A doubleheaded, metal contact 20extends through the center of the bottom wall 14 of the casing 12, andis secured to the bottom wall 14. A bushing 22 of an electricalinsulating material fits between the contact 20 and the bottom wall 14so as to electrically insulate the contact 20 from the bottom wall 14. Aheaded, metal pin 24 extends through the bottom wall 14 spaced radiallyfrom the contact 20. A bimetal switch arm 26 is secured at one end tothe end of the pin 24 which is outside the casing 12. Switch arm 26extends across the contact 20. A contact button 27 is secured to theouter end of the switch arm 26 in alignment with the contact 20. Washers28 of electrical insulating material surround the pin 24 between thebottom wall 14 and the switch arm 26. the switch arm 26 from the bottomwall 14 a distance so that the switch arm 26 is normally spaced from thecontact 20.

A pair of standard 1.5 volt dry cell batteries 30 and 32 are mounted oneabove the other in the casing 12. The batteries 30 and 32 are arrangedin series with the bottom battery 30 seated on the contact 20. Anelectrically actuated alarm device 34 is mounted in the top end por-Washers 28 space tion 16 of the casing 1 2. Alarm device 34 may be ofany well known sound producing type, but preferably comprises anelectric horn. The metal casing of the alarm device 34 has an annularflange 36 which is seated on the top end of the top portion 16 of thecasing 12. A metal spring contact 38 is secured to the alarm device 34by a screw 40. Washers 42 and 44 of electrical insulating materialsurround the screw 40 on opposite sides of the spring contact 30 toelectrically insulate the spring contact 38 from the alarm device 34.Spring contact'38 engages the top terminal of the battery 32 withsufiicient pressure to hold the battery 32 tightly against the battery30, and the battery 30 tightly against the contact 20. A wire 46electrically connects one side of the sound producing mechanism of thealarm device 34 to the spring contact 38. The other side of the soundproducing mechanism of the alarm device 34 is internally connected tothe casing of the alarm device 34, which in turn is electricallyconnected to the switch arm 26 through the casing 12.

A cap, generally designated as 48, is secured to the top end portion 16of the casing 12, and extends across the open end of the casing 12. Cap48'comprises a cylindrical rim 50, anda cover 52. The rim 50 of cap 48is internally threaded to match the external threads on the top endportion 16 of the casing 12. The cover 52 of the cap 48 has a flatperipheral portion 52a which is secured to the rim S0, and a raisedcentral portion 52b. The raised central portion 52b of the cover 52 ofcap 48 has a plurality of holes 54 therethrough. The cap 48 is securedto the casing 12 by threading the rim 50 around the top end portion 16of the casing 12 until the peripheral portion 52a of the cover 52 of cap48 engages the top surface of the flange 36 of the alarm device 34.Thus, the alarm device 34 is securedly mounted to the casing 12.

The fire alarm unit 10 of the present invention is used in the followingmanner:

As shown in FIGURE 1, the fire alarm unit 10 is mounted on a nail orhook 56 secured to a wall 58 by inserting the outer end of the nail orhook 56 through the keyhole slot 18 in the casing 12 of the fire alarmunit 10. The fire alarm unit 10 is thus supported on the wall 58 withthe cover 52 of the cap 48 facing upwardly, and the bottom wall 14 ofthe casing 12 facing downwardly. Since the fire alarm unit 10 isself-contained, it can be easily and quickly mounted anywhere in a roomwithout the necessity for special electrical wiring or the need ofspecial tools or special skill. Also, since the fire alarm unit 10 isrelatively small and compact, it can be easily carried from place toplace if necessary.

In the event of a fire, the heated air from the fire heats the bimetalswitch arm 25 so that the switch arm 26 moves the contact button 27 intoengagement with the contact 20. This completes the electrical circuitthrough the batteries 30 and 32 and the alarm device 34 so that thealarm device 34 is operated to sound an alarm signal. After the fire hasbeen extinguished, and the air around the fire alarm unit 10 has cooleddown, the switch arm 26 will return to its normal position with thecontact button 27 spaced from the contact 20.

To insure that the fire alarm unit 10 is always in good operatingcondition, it is desirable from time-to-time to test the fire alarm unit10, particularly to determine whether the batteries 30 and 32 havesuflicient voltage to operate the alarm device 34. This can be easily accomplished without the necessity of removing the fire alarm unit 10 fromthe wall 58 by merely pressing the contact button 27 against the contact20 to complete the electrical circuit through the batteries 30 and 32and the alarm device 34. When the pressure applied to the conthe casing12 and replaced with fresh batteries.

tact button 27 is released the resiliency of the switch arm 26automatically moves the contact button 27 away from the contact 20. Inthe event that the batteries 30 and 32 become worn out, they can beeasily replaced by removing the cap 48 and lifting out the alarm device34. The batteries 30 and 33 can then be removed from Since there are nowires permanently connecting the alarm device 3.4 with the batteries 30and 32, and with the easing 12, the batteries 30 and 32 can be easilyreplaced without the need of any special tools or special skill.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specification as indicating the scope of theinvention.

I claim:

1. A fire alarm unit comprising a hollow metal casing,

a contact extending through and secured to said casing,

means electrically insulating said contact from said casing, a bimetalswitch arm mechanically and electrically secured to the outside of saidcasing, said switch arm extending across and normally spaced from saidcontact,

batteries in series within said casing, one of said batteries being indirect abutting electrical engagement with 4 ing, said resilient contactbeing electrically connected to said alarm device, and at least oneperforation in a portion of said casing to admit audible signals fromsaid alarm device.

2. A fire alarm unit in accordance with claim 1 wherein said means formechanically and electrically securing said alarm device includes aremovable cover on said casing, said alarm device having a radiallyoutwardly extending flange of sufiicient size so that said flange may beclamped to said casing by said removable cover, and

said cover being the portion of said casing having the perforation toadmit audible signals from said alarm device.

References Cited in the file of this patent UNITED STATES PATENTS1,562,574 Maud Nov. 24, 1925 2,289,128 Kopf July 7, 194-2 7 2,446,794Thornton Aug. 10, 1948 2,514,807 Shaw July 11, 1950 2,786,195 ColetteMar. 19, 1957 2,809,368 Ehlers Oct. 8, 1957 2,816,280 Detweiler Dec. 10,1957 2,819,367 Ouellette Jan. 7, 1958 2,832,949 Pivetz Apr. 29, 19582,911,637 Wortmann Nov. 3, 1959 2,916,915 Burgert Dec. 15, 19592,954,548 I Gould Sept. 27, 1960

